1 /*
2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc_implementation/shared/adaptiveSizePolicy.hpp"
27 #include "gc_implementation/shared/gcPolicyCounters.hpp"
28 #include "gc_implementation/shared/vmGCOperations.hpp"
29 #include "memory/cardTableRS.hpp"
30 #include "memory/collectorPolicy.hpp"
31 #include "memory/gcLocker.inline.hpp"
32 #include "memory/genCollectedHeap.hpp"
33 #include "memory/generationSpec.hpp"
34 #include "memory/space.hpp"
35 #include "memory/universe.hpp"
36 #include "runtime/arguments.hpp"
37 #include "runtime/globals_extension.hpp"
38 #include "runtime/handles.inline.hpp"
39 #include "runtime/java.hpp"
40 #include "runtime/vmThread.hpp"
41 #ifdef TARGET_OS_FAMILY_linux
42 # include "thread_linux.inline.hpp"
43 #endif
44 #ifdef TARGET_OS_FAMILY_solaris
45 # include "thread_solaris.inline.hpp"
46 #endif
47 #ifdef TARGET_OS_FAMILY_windows
48 # include "thread_windows.inline.hpp"
49 #endif
50 #ifdef TARGET_OS_FAMILY_bsd
51 # include "thread_bsd.inline.hpp"
52 #endif
53 #ifndef SERIALGC
54 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp"
55 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp"
56 #endif
57
58 // CollectorPolicy methods.
59
60 void CollectorPolicy::initialize_flags() {
61 if (MetaspaceSize > MaxMetaspaceSize) {
62 MaxMetaspaceSize = MetaspaceSize;
63 }
64 MetaspaceSize = MAX2(min_alignment(), align_size_down_(MetaspaceSize, min_alignment()));
65 // Don't increase Metaspace size limit above specified.
66 MaxMetaspaceSize = align_size_down(MaxMetaspaceSize, max_alignment());
67 if (MetaspaceSize > MaxMetaspaceSize) {
68 MetaspaceSize = MaxMetaspaceSize;
69 }
70
71 MinMetaspaceExpansion = MAX2(min_alignment(), align_size_down_(MinMetaspaceExpansion, min_alignment()));
72 MaxMetaspaceExpansion = MAX2(min_alignment(), align_size_down_(MaxMetaspaceExpansion, min_alignment()));
73
74 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment());
75
76 assert(MetaspaceSize % min_alignment() == 0, "metapace alignment");
77 assert(MaxMetaspaceSize % max_alignment() == 0, "maximum metaspace alignment");
78 if (MetaspaceSize < 256*K) {
79 vm_exit_during_initialization("Too small initial Metaspace size");
80 }
81 }
82
83 void CollectorPolicy::initialize_size_info() {
84 // User inputs from -mx and ms are aligned
85 set_initial_heap_byte_size(InitialHeapSize);
86 if (initial_heap_byte_size() == 0) {
87 set_initial_heap_byte_size(NewSize + OldSize);
88 }
89 set_initial_heap_byte_size(align_size_up(_initial_heap_byte_size,
90 min_alignment()));
91
92 set_min_heap_byte_size(Arguments::min_heap_size());
93 if (min_heap_byte_size() == 0) {
94 set_min_heap_byte_size(NewSize + OldSize);
95 }
96 set_min_heap_byte_size(align_size_up(_min_heap_byte_size,
97 min_alignment()));
98
99 set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));
100
101 // Check heap parameter properties
102 if (initial_heap_byte_size() < M) {
103 vm_exit_during_initialization("Too small initial heap");
104 }
105 // Check heap parameter properties
106 if (min_heap_byte_size() < M) {
107 vm_exit_during_initialization("Too small minimum heap");
108 }
109 if (initial_heap_byte_size() <= NewSize) {
110 // make sure there is at least some room in old space
111 vm_exit_during_initialization("Too small initial heap for new size specified");
112 }
113 if (max_heap_byte_size() < min_heap_byte_size()) {
114 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
115 }
116 if (initial_heap_byte_size() < min_heap_byte_size()) {
117 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
118 }
119 if (max_heap_byte_size() < initial_heap_byte_size()) {
120 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
121 }
122
123 if (PrintGCDetails && Verbose) {
124 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
125 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
126 min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size());
127 }
128 }
129
130 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
131 bool result = _should_clear_all_soft_refs;
132 set_should_clear_all_soft_refs(false);
133 return result;
134 }
135
136 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
137 int max_covered_regions) {
138 switch (rem_set_name()) {
139 case GenRemSet::CardTable: {
140 CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);
141 return res;
142 }
143 default:
144 guarantee(false, "unrecognized GenRemSet::Name");
145 return NULL;
146 }
147 }
148
149 void CollectorPolicy::cleared_all_soft_refs() {
150 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
151 // have been cleared in the last collection but if the gc overhear
152 // limit continues to be near, SoftRefs should still be cleared.
153 if (size_policy() != NULL) {
154 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
155 }
156 _all_soft_refs_clear = true;
157 }
158
159
160 // GenCollectorPolicy methods.
161
162 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
163 size_t x = base_size / (NewRatio+1);
164 size_t new_gen_size = x > min_alignment() ?
165 align_size_down(x, min_alignment()) :
166 min_alignment();
167 return new_gen_size;
168 }
169
170 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
171 size_t maximum_size) {
172 size_t alignment = min_alignment();
173 size_t max_minus = maximum_size - alignment;
174 return desired_size < max_minus ? desired_size : max_minus;
175 }
176
177
178 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
179 size_t init_promo_size,
180 size_t init_survivor_size) {
181 const double max_gc_minor_pause_sec = ((double) MaxGCMinorPauseMillis)/1000.0;
182 _size_policy = new AdaptiveSizePolicy(init_eden_size,
183 init_promo_size,
184 init_survivor_size,
185 max_gc_minor_pause_sec,
186 GCTimeRatio);
187 }
188
189 size_t GenCollectorPolicy::compute_max_alignment() {
190 // The card marking array and the offset arrays for old generations are
191 // committed in os pages as well. Make sure they are entirely full (to
192 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
193 // byte entry and the os page size is 4096, the maximum heap size should
194 // be 512*4096 = 2MB aligned.
195 size_t alignment = GenRemSet::max_alignment_constraint(rem_set_name());
196
197 // Parallel GC does its own alignment of the generations to avoid requiring a
198 // large page (256M on some platforms) for the permanent generation. The
199 // other collectors should also be updated to do their own alignment and then
200 // this use of lcm() should be removed.
201 if (UseLargePages && !UseParallelGC) {
202 // in presence of large pages we have to make sure that our
203 // alignment is large page aware
204 alignment = lcm(os::large_page_size(), alignment);
205 }
206
207 return alignment;
208 }
209
210 void GenCollectorPolicy::initialize_flags() {
211 // All sizes must be multiples of the generation granularity.
212 set_min_alignment((uintx) Generation::GenGrain);
213 set_max_alignment(compute_max_alignment());
214 assert(max_alignment() >= min_alignment() &&
215 max_alignment() % min_alignment() == 0,
216 "invalid alignment constraints");
217
218 CollectorPolicy::initialize_flags();
219
220 // All generational heaps have a youngest gen; handle those flags here.
221
222 // Adjust max size parameters
223 if (NewSize > MaxNewSize) {
224 MaxNewSize = NewSize;
225 }
226 NewSize = align_size_down(NewSize, min_alignment());
227 MaxNewSize = align_size_down(MaxNewSize, min_alignment());
228
229 // Check validity of heap flags
230 assert(NewSize % min_alignment() == 0, "eden space alignment");
231 assert(MaxNewSize % min_alignment() == 0, "survivor space alignment");
232
233 if (NewSize < 3*min_alignment()) {
234 // make sure there room for eden and two survivor spaces
235 vm_exit_during_initialization("Too small new size specified");
236 }
237 if (SurvivorRatio < 1 || NewRatio < 1) {
238 vm_exit_during_initialization("Invalid heap ratio specified");
239 }
240 }
241
242 void TwoGenerationCollectorPolicy::initialize_flags() {
243 GenCollectorPolicy::initialize_flags();
244
245 OldSize = align_size_down(OldSize, min_alignment());
246 if (NewSize + OldSize > MaxHeapSize) {
247 MaxHeapSize = NewSize + OldSize;
248 }
249 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
250
251 always_do_update_barrier = UseConcMarkSweepGC;
252
253 // Check validity of heap flags
254 assert(OldSize % min_alignment() == 0, "old space alignment");
255 assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment");
256 }
257
258 // Values set on the command line win over any ergonomically
259 // set command line parameters.
260 // Ergonomic choice of parameters are done before this
261 // method is called. Values for command line parameters such as NewSize
262 // and MaxNewSize feed those ergonomic choices into this method.
263 // This method makes the final generation sizings consistent with
264 // themselves and with overall heap sizings.
265 // In the absence of explicitly set command line flags, policies
266 // such as the use of NewRatio are used to size the generation.
267 void GenCollectorPolicy::initialize_size_info() {
268 CollectorPolicy::initialize_size_info();
269
270 // min_alignment() is used for alignment within a generation.
271 // There is additional alignment done down stream for some
272 // collectors that sometimes causes unwanted rounding up of
273 // generations sizes.
274
275 // Determine maximum size of gen0
276
277 size_t max_new_size = 0;
278 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
279 if (MaxNewSize < min_alignment()) {
280 max_new_size = min_alignment();
281 }
282 if (MaxNewSize >= max_heap_byte_size()) {
283 max_new_size = align_size_down(max_heap_byte_size() - min_alignment(),
284 min_alignment());
285 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
286 "greater than the entire heap (" SIZE_FORMAT "k). A "
287 "new generation size of " SIZE_FORMAT "k will be used.",
288 MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K);
289 } else {
290 max_new_size = align_size_down(MaxNewSize, min_alignment());
291 }
292
293 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
294 // specially at this point to just use an ergonomically set
295 // MaxNewSize to set max_new_size. For cases with small
296 // heaps such a policy often did not work because the MaxNewSize
297 // was larger than the entire heap. The interpretation given
298 // to ergonomically set flags is that the flags are set
299 // by different collectors for their own special needs but
300 // are not allowed to badly shape the heap. This allows the
301 // different collectors to decide what's best for themselves
302 // without having to factor in the overall heap shape. It
303 // can be the case in the future that the collectors would
304 // only make "wise" ergonomics choices and this policy could
305 // just accept those choices. The choices currently made are
306 // not always "wise".
307 } else {
308 max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size());
309 // Bound the maximum size by NewSize below (since it historically
310 // would have been NewSize and because the NewRatio calculation could
311 // yield a size that is too small) and bound it by MaxNewSize above.
312 // Ergonomics plays here by previously calculating the desired
313 // NewSize and MaxNewSize.
314 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
315 }
316 assert(max_new_size > 0, "All paths should set max_new_size");
317
318 // Given the maximum gen0 size, determine the initial and
319 // minimum gen0 sizes.
320
321 if (max_heap_byte_size() == min_heap_byte_size()) {
322 // The maximum and minimum heap sizes are the same so
323 // the generations minimum and initial must be the
324 // same as its maximum.
325 set_min_gen0_size(max_new_size);
326 set_initial_gen0_size(max_new_size);
327 set_max_gen0_size(max_new_size);
328 } else {
329 size_t desired_new_size = 0;
330 if (!FLAG_IS_DEFAULT(NewSize)) {
331 // If NewSize is set ergonomically (for example by cms), it
332 // would make sense to use it. If it is used, also use it
333 // to set the initial size. Although there is no reason
334 // the minimum size and the initial size have to be the same,
335 // the current implementation gets into trouble during the calculation
336 // of the tenured generation sizes if they are different.
337 // Note that this makes the initial size and the minimum size
338 // generally small compared to the NewRatio calculation.
339 _min_gen0_size = NewSize;
340 desired_new_size = NewSize;
341 max_new_size = MAX2(max_new_size, NewSize);
342 } else {
343 // For the case where NewSize is the default, use NewRatio
344 // to size the minimum and initial generation sizes.
345 // Use the default NewSize as the floor for these values. If
346 // NewRatio is overly large, the resulting sizes can be too
347 // small.
348 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()),
349 NewSize);
350 desired_new_size =
351 MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()),
352 NewSize);
353 }
354
355 assert(_min_gen0_size > 0, "Sanity check");
356 set_initial_gen0_size(desired_new_size);
357 set_max_gen0_size(max_new_size);
358
359 // At this point the desirable initial and minimum sizes have been
360 // determined without regard to the maximum sizes.
361
362 // Bound the sizes by the corresponding overall heap sizes.
363 set_min_gen0_size(
364 bound_minus_alignment(_min_gen0_size, min_heap_byte_size()));
365 set_initial_gen0_size(
366 bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size()));
367 set_max_gen0_size(
368 bound_minus_alignment(_max_gen0_size, max_heap_byte_size()));
369
370 // At this point all three sizes have been checked against the
371 // maximum sizes but have not been checked for consistency
372 // among the three.
373
374 // Final check min <= initial <= max
375 set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size));
376 set_initial_gen0_size(
377 MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size));
378 set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size));
379 }
380
381 if (PrintGCDetails && Verbose) {
382 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
383 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
384 min_gen0_size(), initial_gen0_size(), max_gen0_size());
385 }
386 }
387
388 // Call this method during the sizing of the gen1 to make
389 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
390 // the most freedom in sizing because it is done before the
391 // policy for gen1 is applied. Once gen1 policies have been applied,
392 // there may be conflicts in the shape of the heap and this method
393 // is used to make the needed adjustments. The application of the
394 // policies could be more sophisticated (iterative for example) but
395 // keeping it simple also seems a worthwhile goal.
396 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
397 size_t* gen1_size_ptr,
398 size_t heap_size,
399 size_t min_gen0_size) {
400 bool result = false;
401 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
402 if (((*gen0_size_ptr + OldSize) > heap_size) &&
403 (heap_size - min_gen0_size) >= min_alignment()) {
404 // Adjust gen0 down to accomodate OldSize
405 *gen0_size_ptr = heap_size - min_gen0_size;
406 *gen0_size_ptr =
407 MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),
408 min_alignment());
409 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
410 result = true;
411 } else {
412 *gen1_size_ptr = heap_size - *gen0_size_ptr;
413 *gen1_size_ptr =
414 MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),
415 min_alignment());
416 }
417 }
418 return result;
419 }
420
421 // Minimum sizes of the generations may be different than
422 // the initial sizes. An inconsistently is permitted here
423 // in the total size that can be specified explicitly by
424 // command line specification of OldSize and NewSize and
425 // also a command line specification of -Xms. Issue a warning
426 // but allow the values to pass.
427
428 void TwoGenerationCollectorPolicy::initialize_size_info() {
429 GenCollectorPolicy::initialize_size_info();
430
431 // At this point the minimum, initial and maximum sizes
432 // of the overall heap and of gen0 have been determined.
433 // The maximum gen1 size can be determined from the maximum gen0
434 // and maximum heap size since no explicit flags exits
435 // for setting the gen1 maximum.
436 _max_gen1_size = max_heap_byte_size() - _max_gen0_size;
437 _max_gen1_size =
438 MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),
439 min_alignment());
440 // If no explicit command line flag has been set for the
441 // gen1 size, use what is left for gen1.
442 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
443 // The user has not specified any value or ergonomics
444 // has chosen a value (which may or may not be consistent
445 // with the overall heap size). In either case make
446 // the minimum, maximum and initial sizes consistent
447 // with the gen0 sizes and the overall heap sizes.
448 assert(min_heap_byte_size() > _min_gen0_size,
449 "gen0 has an unexpected minimum size");
450 set_min_gen1_size(min_heap_byte_size() - min_gen0_size());
451 set_min_gen1_size(
452 MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),
453 min_alignment()));
454 set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());
455 set_initial_gen1_size(
456 MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),
457 min_alignment()));
458
459 } else {
460 // It's been explicitly set on the command line. Use the
461 // OldSize and then determine the consequences.
462 set_min_gen1_size(OldSize);
463 set_initial_gen1_size(OldSize);
464
465 // If the user has explicitly set an OldSize that is inconsistent
466 // with other command line flags, issue a warning.
467 // The generation minimums and the overall heap mimimum should
468 // be within one heap alignment.
469 if ((_min_gen1_size + _min_gen0_size + min_alignment()) <
470 min_heap_byte_size()) {
471 warning("Inconsistency between minimum heap size and minimum "
472 "generation sizes: using minimum heap = " SIZE_FORMAT,
473 min_heap_byte_size());
474 }
475 if ((OldSize > _max_gen1_size)) {
476 warning("Inconsistency between maximum heap size and maximum "
477 "generation sizes: using maximum heap = " SIZE_FORMAT
478 " -XX:OldSize flag is being ignored",
479 max_heap_byte_size());
480 }
481 // If there is an inconsistency between the OldSize and the minimum and/or
482 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
483 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
484 min_heap_byte_size(), OldSize)) {
485 if (PrintGCDetails && Verbose) {
486 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
487 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
488 min_gen0_size(), initial_gen0_size(), max_gen0_size());
489 }
490 }
491 // Initial size
492 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
493 initial_heap_byte_size(), OldSize)) {
494 if (PrintGCDetails && Verbose) {
495 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
496 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
497 min_gen0_size(), initial_gen0_size(), max_gen0_size());
498 }
499 }
500 }
501 // Enforce the maximum gen1 size.
502 set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));
503
504 // Check that min gen1 <= initial gen1 <= max gen1
505 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));
506 set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));
507
508 if (PrintGCDetails && Verbose) {
509 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
510 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
511 min_gen1_size(), initial_gen1_size(), max_gen1_size());
512 }
513 }
514
515 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
516 bool is_tlab,
517 bool* gc_overhead_limit_was_exceeded) {
518 GenCollectedHeap *gch = GenCollectedHeap::heap();
519
520 debug_only(gch->check_for_valid_allocation_state());
521 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
522
523 // In general gc_overhead_limit_was_exceeded should be false so
524 // set it so here and reset it to true only if the gc time
525 // limit is being exceeded as checked below.
526 *gc_overhead_limit_was_exceeded = false;
527
528 HeapWord* result = NULL;
529
530 // Loop until the allocation is satisified,
531 // or unsatisfied after GC.
532 for (int try_count = 1; /* return or throw */; try_count += 1) {
533 HandleMark hm; // discard any handles allocated in each iteration
534
535 // First allocation attempt is lock-free.
536 Generation *gen0 = gch->get_gen(0);
537 assert(gen0->supports_inline_contig_alloc(),
538 "Otherwise, must do alloc within heap lock");
539 if (gen0->should_allocate(size, is_tlab)) {
540 result = gen0->par_allocate(size, is_tlab);
541 if (result != NULL) {
542 assert(gch->is_in_reserved(result), "result not in heap");
543 return result;
544 }
545 }
546 unsigned int gc_count_before; // read inside the Heap_lock locked region
547 {
548 MutexLocker ml(Heap_lock);
549 if (PrintGC && Verbose) {
550 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
551 " attempting locked slow path allocation");
552 }
553 // Note that only large objects get a shot at being
554 // allocated in later generations.
555 bool first_only = ! should_try_older_generation_allocation(size);
556
557 result = gch->attempt_allocation(size, is_tlab, first_only);
558 if (result != NULL) {
559 assert(gch->is_in_reserved(result), "result not in heap");
560 return result;
561 }
562
563 if (GC_locker::is_active_and_needs_gc()) {
564 if (is_tlab) {
565 return NULL; // Caller will retry allocating individual object
566 }
567 if (!gch->is_maximal_no_gc()) {
568 // Try and expand heap to satisfy request
569 result = expand_heap_and_allocate(size, is_tlab);
570 // result could be null if we are out of space
571 if (result != NULL) {
572 return result;
573 }
574 }
575
576 // If this thread is not in a jni critical section, we stall
577 // the requestor until the critical section has cleared and
578 // GC allowed. When the critical section clears, a GC is
579 // initiated by the last thread exiting the critical section; so
580 // we retry the allocation sequence from the beginning of the loop,
581 // rather than causing more, now probably unnecessary, GC attempts.
582 JavaThread* jthr = JavaThread::current();
583 if (!jthr->in_critical()) {
584 MutexUnlocker mul(Heap_lock);
585 // Wait for JNI critical section to be exited
586 GC_locker::stall_until_clear();
587 continue;
588 } else {
589 if (CheckJNICalls) {
590 fatal("Possible deadlock due to allocating while"
591 " in jni critical section");
592 }
593 return NULL;
594 }
595 }
596
597 // Read the gc count while the heap lock is held.
598 gc_count_before = Universe::heap()->total_collections();
599 }
600
601 VM_GenCollectForAllocation op(size,
602 is_tlab,
603 gc_count_before);
604 VMThread::execute(&op);
605 if (op.prologue_succeeded()) {
606 result = op.result();
607 if (op.gc_locked()) {
608 assert(result == NULL, "must be NULL if gc_locked() is true");
609 continue; // retry and/or stall as necessary
610 }
611
612 // Allocation has failed and a collection
613 // has been done. If the gc time limit was exceeded the
614 // this time, return NULL so that an out-of-memory
615 // will be thrown. Clear gc_overhead_limit_exceeded
616 // so that the overhead exceeded does not persist.
617
618 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
619 const bool softrefs_clear = all_soft_refs_clear();
620 assert(!limit_exceeded || softrefs_clear, "Should have been cleared");
621 if (limit_exceeded && softrefs_clear) {
622 *gc_overhead_limit_was_exceeded = true;
623 size_policy()->set_gc_overhead_limit_exceeded(false);
624 if (op.result() != NULL) {
625 CollectedHeap::fill_with_object(op.result(), size);
626 }
627 return NULL;
628 }
629 assert(result == NULL || gch->is_in_reserved(result),
630 "result not in heap");
631 return result;
632 }
633
634 // Give a warning if we seem to be looping forever.
635 if ((QueuedAllocationWarningCount > 0) &&
636 (try_count % QueuedAllocationWarningCount == 0)) {
637 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
638 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
639 }
640 }
641 }
642
643 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
644 bool is_tlab) {
645 GenCollectedHeap *gch = GenCollectedHeap::heap();
646 HeapWord* result = NULL;
647 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
648 Generation *gen = gch->get_gen(i);
649 if (gen->should_allocate(size, is_tlab)) {
650 result = gen->expand_and_allocate(size, is_tlab);
651 }
652 }
653 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
654 return result;
655 }
656
657 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
658 bool is_tlab) {
659 GenCollectedHeap *gch = GenCollectedHeap::heap();
660 GCCauseSetter x(gch, GCCause::_allocation_failure);
661 HeapWord* result = NULL;
662
663 assert(size != 0, "Precondition violated");
664 if (GC_locker::is_active_and_needs_gc()) {
665 // GC locker is active; instead of a collection we will attempt
666 // to expand the heap, if there's room for expansion.
667 if (!gch->is_maximal_no_gc()) {
668 result = expand_heap_and_allocate(size, is_tlab);
669 }
670 return result; // could be null if we are out of space
671 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
672 // Do an incremental collection.
673 gch->do_collection(false /* full */,
674 false /* clear_all_soft_refs */,
675 size /* size */,
676 is_tlab /* is_tlab */,
677 number_of_generations() - 1 /* max_level */);
678 } else {
679 if (Verbose && PrintGCDetails) {
680 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
681 }
682 // Try a full collection; see delta for bug id 6266275
683 // for the original code and why this has been simplified
684 // with from-space allocation criteria modified and
685 // such allocation moved out of the safepoint path.
686 gch->do_collection(true /* full */,
687 false /* clear_all_soft_refs */,
688 size /* size */,
689 is_tlab /* is_tlab */,
690 number_of_generations() - 1 /* max_level */);
691 }
692
693 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
694
695 if (result != NULL) {
696 assert(gch->is_in_reserved(result), "result not in heap");
697 return result;
698 }
699
700 // OK, collection failed, try expansion.
701 result = expand_heap_and_allocate(size, is_tlab);
702 if (result != NULL) {
703 return result;
704 }
705
706 // If we reach this point, we're really out of memory. Try every trick
707 // we can to reclaim memory. Force collection of soft references. Force
708 // a complete compaction of the heap. Any additional methods for finding
709 // free memory should be here, especially if they are expensive. If this
710 // attempt fails, an OOM exception will be thrown.
711 {
712 IntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
713
714 gch->do_collection(true /* full */,
715 true /* clear_all_soft_refs */,
716 size /* size */,
717 is_tlab /* is_tlab */,
718 number_of_generations() - 1 /* max_level */);
719 }
720
721 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
722 if (result != NULL) {
723 assert(gch->is_in_reserved(result), "result not in heap");
724 return result;
725 }
726
727 assert(!should_clear_all_soft_refs(),
728 "Flag should have been handled and cleared prior to this point");
729
730 // What else? We might try synchronous finalization later. If the total
731 // space available is large enough for the allocation, then a more
732 // complete compaction phase than we've tried so far might be
733 // appropriate.
734 return NULL;
735 }
736
737 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
738 ClassLoaderData* loader_data,
739 size_t word_size,
740 Metaspace::MetadataType mdtype) {
741 uint loop_count = 0;
742 uint gc_count = 0;
743 uint full_gc_count = 0;
744
745 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
746
747 do {
748 MetaWord* result = NULL;
749 if (GC_locker::is_active_and_needs_gc()) {
750 // If the GC_locker is active, just expand and allocate.
751 // If that does not succeed, wait if this thread is not
752 // in a critical section itself.
753 result =
754 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
755 mdtype);
756 if (result != NULL) {
757 return result;
758 }
759 JavaThread* jthr = JavaThread::current();
760 if (!jthr->in_critical()) {
761 // Wait for JNI critical section to be exited
762 GC_locker::stall_until_clear();
763 // The GC invoked by the last thread leaving the critical
764 // section will be a young collection and a full collection
765 // is (currently) needed for unloading classes so continue
766 // to the next iteration to get a full GC.
767 continue;
768 } else {
769 if (CheckJNICalls) {
770 fatal("Possible deadlock due to allocating while"
771 " in jni critical section");
772 }
773 return NULL;
774 }
775 }
776
777 { // Need lock to get self consistent gc_count's
778 MutexLocker ml(Heap_lock);
779 gc_count = Universe::heap()->total_collections();
780 full_gc_count = Universe::heap()->total_full_collections();
781 }
782
783 // Generate a VM operation
784 VM_CollectForMetadataAllocation op(loader_data,
785 word_size,
786 mdtype,
787 gc_count,
788 full_gc_count,
789 GCCause::_metadata_GC_threshold);
790 VMThread::execute(&op);
791 if (op.prologue_succeeded()) {
792 return op.result();
793 }
794 loop_count++;
795 if ((QueuedAllocationWarningCount > 0) &&
796 (loop_count % QueuedAllocationWarningCount == 0)) {
797 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
798 " size=%d", loop_count, word_size);
799 }
800 } while (true); // Until a GC is done
801 }
802
803 // Return true if any of the following is true:
804 // . the allocation won't fit into the current young gen heap
805 // . gc locker is occupied (jni critical section)
806 // . heap memory is tight -- the most recent previous collection
807 // was a full collection because a partial collection (would
808 // have) failed and is likely to fail again
809 bool GenCollectorPolicy::should_try_older_generation_allocation(
810 size_t word_size) const {
811 GenCollectedHeap* gch = GenCollectedHeap::heap();
812 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
813 return (word_size > heap_word_size(gen0_capacity))
814 || GC_locker::is_active_and_needs_gc()
815 || gch->incremental_collection_failed();
816 }
817
818
819 //
820 // MarkSweepPolicy methods
821 //
822
823 MarkSweepPolicy::MarkSweepPolicy() {
824 initialize_all();
825 }
826
827 void MarkSweepPolicy::initialize_generations() {
828 _generations = new GenerationSpecPtr[number_of_generations()];
829 if (_generations == NULL)
830 vm_exit_during_initialization("Unable to allocate gen spec");
831
832 if (UseParNewGC && ParallelGCThreads > 0) {
833 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
834 } else {
835 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
836 }
837 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
838
839 if (_generations[0] == NULL || _generations[1] == NULL)
840 vm_exit_during_initialization("Unable to allocate gen spec");
841 }
842
843 void MarkSweepPolicy::initialize_gc_policy_counters() {
844 // initialize the policy counters - 2 collectors, 3 generations
845 if (UseParNewGC && ParallelGCThreads > 0) {
846 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
847 }
848 else {
849 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
850 }
851 }